1. Field of the Invention
The invention is related to the field of glide test systems and, in particular, to a glide test head that incorporates heating elements to create a substantially planar surface on the glide test head.
2. Statement of the Problem
Many computer systems use magnetic disk drives for mass storage of information. Magnetic disk drives typically include one or more magnetic recording heads (sometimes referred to as sliders) that include read elements and write elements. An actuator/suspension arm holds the recording head above a magnetic disk. When the magnetic disk rotates, an air flow generated by the rotation of the magnetic disk causes an air bearing surface (ABS) side of the recording head to fly a particular height above the magnetic disk. The fly height depends on the shape of the ABS. As the recording head flies on the air bearing, an actuator moves an actuator/suspension arm to position the read element and the write element over selected tracks of the magnetic disk.
The magnetic disks are typically manufactured by sputtering a plurality of layers onto a substrate, such as a magnetic recording layer, an overcoat, a lubricant layer, etc. After the sputtering process, small protrusions may exist on the surface of the magnetic disk. These small protrusions are referred to as asperities. To remove the asperities from the surface of the magnetic disk, a burnishing process is performed.
For the burnishing process, a burnishing head is formed on a trailing end of a burnishing slider. The burnishing head is then placed in contact with the surface of the magnetic disk while the magnetic disk is rotated. The burnishing head is moved from the inner radius of the magnetic disk to the outer radius of the magnetic disk to remove asperities on the surface of the disk. However, some of the asperities may not be removed by the burnishing process, so a glide testing process is then performed to detect whether asperities remain on the surface of the magnetic disk.
For the glide testing process, the magnetic disk is placed in a glide test system which resembles a disk drive. The glide test system includes a glide test head having an air bearing surface (ABS). The glide test head is similar to a slider, but does not include a read and write element on a trailing end as does a slider. Instead, the glide test head includes a detection pad on its trailing end. The detection pad has a detection surface that is parallel to the ABS and is adapted to contact asperities that protrude from the surface of the magnetic disk. The glide test head also includes a sensing element, such as a piezoelectric sensor.
To perform glide testing on the magnetic disk, the magnetic disk is rotated and the glide test head flies a particular height above the magnetic disk. The height at which the glide test head flies is referred to as the glide height. The ABS of the glide test head is formed so that the glide height of the glide test head is dependent on the velocity at which the magnetic disk is rotated. Thus, the velocity is adjusted to position the glide test head at a desired glide height. A typical glide height presently used is 6 nanometers. If an asperity exists on the surface of the magnetic disk, then the asperity will contact the detection surface of the detection pad. The contact with the asperity creates a vibration in the glide test head which is detected by the sensing element. If asperities are detected on the surface of the magnetic disk, then the magnetic disk may be burnished another time, or may be discarded.
One problem with present glide testing is that the detection surface may not be sufficiently flat to accurately detect asperities on the magnetic disk. The width of a detection pad on a typical glide test head may be 100 microns to 300 microns. Over these widths, there may be an uneven topography (e.g., slight curves, rolls, or ripples) along the detection surface due to normal imperfections in the fabrication processes. Over a width of 100-300 microns, it is common for the topography of the detection surface to have a 2 nanometer peak-to-peak variation, or even more. When the desired glide height is around 6 nanometers, a 2 nanometer variation along the detection surface may negatively affect the quality of the glide testing process.